If you working on electronics about 35 years (like me for example) you have a lot of chances to see new things!
One of these things was that, to replace my toroid transformer in my 20 years preamplifier (Diy Hi-End) with R-CORE.
The reasons was two!
First, when i put my ears very close to toroidal trafo, i was hear hum noise!
In the past i never checked to hear that, and second reason after a lot of reviews all around the audio forums, i was thinking that, it is not a bad idea with this little cost to make a change!
Everything for experiments! That's the life!
The most important there is no hum noise, second i am not sure but i believe something has change to the better way!